1. Field of the Invention
The present invention relates to an occlusion device consisting of a braiding of thin wires given a suitable form by means of a molding and heat treatment procedure and which tapers to the diameter of a catheter used for an intravascular implantation or explantation procedure having a proximal retention area, a distal retention area, at which the ends of the wires or threads converge into a holder, and having a cylindrical crosspiece interposed between said proximal retention area and said distal retention area, whereby the two retention areas position on the two sides of a shunt to be occluded in a septum following implantation while the crosspiece transverses the shunt. The invention moreover relates to a surgical instrument for the implantation and explantation of an implant, in particular an occlusion device as described above. Lastly, the present invention relates to a method for the repeated coupling of an implant, in particular an occlusion device as described above, to such a surgical instrument.
2. Description of the Related Art
Medical technology has long endeavored to be able to occlude septal defects, for instance atrioseptal defects, by means of non-surgical transvenous catheter procedures, in other words, without having to perform an operation in the literal sense. Various different occlusion systems have been proposed to this end, each with their own pros and cons, without any one specific occlusion system having yet become widely accepted. In making reference to these different systems, the following will use the terms “occluder” or “occlusion device.” In all interventional occlusion systems, a self-expanding umbrella system is introduced transvenously into a defect to be occluded in a septum. This type of system might comprise two umbrellas; one positioned, for example, at the distal side of the septum (i.e., the side furthest from the median plane of the body/heart) and one at the proximal side of the septum (i.e., the side closer to the median plane of the body), whereby the two umbrella prostheses are subsequently secured to a double umbrella in the septal defect. Thus, in the assembled state, the occlusion system usually consists of two clamped umbrellas connected to one another by means of a short bolt transversing the defect. However, a disadvantage to such prior art occlusion devices turns out to be the relatively complicated, difficult and complex implantation procedure. Apart from the complicated implantation of the occlusion system in the septal defect to be occluded, the umbrellas utilized are susceptible to material fatigue along with fragment fracture. Furthermore, thromboembolic complications are frequently to be anticipated.
In order to enable the inventive occlusion device to be introduced by means of a surgical insertion instrument and/or guidewire, a holder is provided at the end of the distal retention area which can engage with the insertion instrument and/or guidewire. It is thereby provided for this engagement to be readily disengaged after positioning the occlusion device in the defect. For example, it is possible to devise the braiding at the end of the distal retention area of the occlusion device in such a manner so as to create an internal threading in the holder to engage with the insertion instrument.
In previously-known occluders made of a nitinol wire braiding, for example from AGA or JEN.meditec, the coupling to the insertion wire is configured as a screw threading. The insertion wire provides for the occluder to be urged forward or backward within the catheter tube. After the occluder has been positioned in the septum of the heart, the insertion wire is unscrewed and the occluder ultimately released. No corrections are thereafter possible.
Since the insertion wire and the coupling are relatively rigid and the catheter approaches the septum of the heart at a shallow angle in the minimally invasive implantation of the occluder through the leg artery for anatomical reasons, the occluder remains tilted upon its unfolding and the umbrellas cannot abut both sides of the shunt. In a situation such as this, the operating surgeon cannot discern whether the occluder will assume its predetermined fit once uncoupled. This gives rise to great uncertainty for the surgeon, in particular since his only means of repositioning an uncoupled occluder is a non-minimally invasive procedure.
The present invention is based on minimizing these crucial disadvantages of the known systems, namely by allowing the occluder all freedom of movement for its independent unfolding and adapting to the septal defect to be occluded after its having been positioned in the septum of the heart and released from the insertion port, and not having it be forced into a position by the insertion instrument which it would not automatically assume by itself and yet having it be repositionable and retrievable with a insertion instrument as necessary.
Of course, other embodiments are also conceivable here as well. With another type of occlusion device, the so-called Lock-Clamshell umbrella system, two stainless steel preferably Dacron-covered umbrellas are provided, each stabilized by four arms. This type of occluder is implanted into the patient through a vein. However, seen as problematic with the Lock-Clamshell occluder is the fact that the insertion instruments necessary to implant the device need to be of relatively large size. A further disadvantage seen with other systems, e.g. the so-called “Amplatz occluder,” is that many different occluder sizes are needed in order to cope with the respective dimensions of the septal defects to be occluded. It thus turns out that the umbrellas do not flatten out completely in the inserted state if the length or the diameter of the crosspiece inserted into the defect is not of an optimum fit. This results in incomplete endothelialization. It has furthermore been shown that many of the systems implanted into patients' bodies exhibit material fatigue and fractures in the metallic structures due to the substantial mechanical stresses over a longer period. This is especially the case given permanent stress between an implant and the septum.
In order to overcome these disadvantages, self-centering occlusion devices have been developed which are inserted into the body of the patient and introduced into the septal defect to be occluded by way of a minimally invasive procedure, for example using a catheter and guidewires. Their design is based on the principle that the occlusion device can be tapered to the dimensions of the insertion instrument and/or catheter used for the intravascular procedure. Such a tapered occlusion device is then introduced by catheter into the septal defect to be occluded, respectively into the shunt of the septal defect to be occluded. The occluder is then discharged from the catheter, upon which the self-expanding umbrellas, retention plates respectively, subsequently unfold against the two sides of the septum. The umbrellas in turn comprise fabric inserts made from or covered by, for example, Dacron, with which the defect/shunt is occluded. The implants remaining in the body are more or less completely ingrown by the body's own tissue after a few weeks or months.
An example of a self-centering occlusion device of the type specified at the outset and in accordance with the prior art is known from WO 99/12478 A1, which is a further development of the occlusion device known as the “Amplatz occluder” in accordance with U.S. Pat. No. 5,725,552. Same consists of a braiding of a plurality of fine, intertwined nitinol wire strands in the shape of a yo-yo. Each braiding is produced in its original form as a rounded braiding having loose wire ends both at its leading end (its proximal side, respectively) as well as at its trailing end (its distal side, respectively). During the subsequent processing of the rounded braiding, each of these loose ends must then be gathered into a sleeve and welded together. After such appropriate processing, both the proximal side as well as the distal side of the finished occluder exhibit a protruding collar. Dacron patches are sewn into the distal and proximal retention umbrellas and the interposed crosspiece. Because of the “memory effect” exhibited by the nitinol material used, the two retention umbrellas unfold by themselves upon exiting the catheter, initially in a balloon-like intermediate stage, whereby the retention umbrellas ultimately positioned on the two sides of the septum eventually assume a more or less flattened form. The crosspiece centers itself automatically into the shunt to be occluded as the umbrellas unfold. Because the collar protrudes past the proximal retention area of the occluder, the problem can arise that the inserted implant causes embolic-related problems, in particular consecutive embolization. Furthermore, a complete endothelialization of occluder implant is often hindered.
An occlusion device made of wire braiding is furthermore known from WO 95/27448 A1. This device, however, does not have a holder such that this occluder cannot be guided during introduction by an insertion instrument in the same way as is the case with the devices described above, nor can it be—in the case of a poor seating—retracted again prior to being uncoupled.
The problem therefore set out for the present invention is to refine such a braided self-centering occlusion device as known to medical technology such that the disadvantages cited above will be overcome. A particular objective is the providing of an occlusion device applicable to occluding defects of different sizes, whereby implantation of the occluder is to be a simple matter and with which explantation is also possible; e.g. to correct improper seating.